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Tech
Sheet Explanation
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The
following is an explanation of some of the categories listed on your racquet’s
technical sheet.
Should
you have any questions please feel free to Contact
Us.
Technical
Explanation
-
Head size: The hitting
area of the racquet, measured in square inches (in2)
and square centimeters (cm2).
Most racquets fall into one of four categories: mid-size (Mid) less
than 95 in2,
mid-plus (MP) 95 to 104 in2,
oversize (OS) 105 to 115 in2,
and super over-size (SOS) 116 in2
and above.
-
Actual grip size: The
actual circumference of the racquet grip measured in inches and millimeters.
The number in parenthesis is the manufacturer’s stated grip circumference.
-
Racquet Number: Each racquet
is numbered on the butt cap and the inside of the throat. This allows
me to track the performance of each racquet.
-
Racquet beam:
The actual beam / width of the racquet measured in millimeters.
The head is measured at the 12, 3, and 5 o’clock position. The
throat is measure mid length.
-
Existing stringed stiffness:
If your strings were not broken we are able to measure the current stringbed
stiffness (deflection) and dynamic tension.
-
Potential energy remaining:
By comparing the original stringbed deflection with the current stringbed
deflection, the RDC is able to calculate the strings current energy
level.
- Unstrung
and strung string diameter: All string gauges are not
the same, therefore SRS measures the actual string diameter prior to
stringing and after the racquet is strung.
-
Stringbed stiffness: Stringbed
stiffness is measured on the Babolat Racquet Diagnostic Center (RDC).
The RDC is a plunger type device the measures stringbed deflection in
the center of the stringbed. Since it is almost impossible to measure
actual stringbed tension Babolat has devised an artificial measurement
index (RDC units). The initial stringbed measurement coupled with the
strung tension gives an accurate indication of the overall tightness
of the stringbed. The RDC is also useful in measuring the decrease in
tension over time. The RDC measurement compares the original reading
with the current reading then determines approximately how much “life”
or potential energy is left in the stringbed.
-
Stringing machine tensions:
There are 2 basic type of stringing machines: spring release and constant
pull. Both machines work well and can produce consistent and reliable
results. SRS uses only electronic constant pull machines. These machines
produce the most accurate / true tension and consequently our indicated
tensions are usually lower than other stringing machines. The indicated
tension can vary by as much 20%. New racquets or racquets with new bumper
& grommets are strung 2 lbs tighter to accommodate the settling
of the bumper and grommets.
-
Dynamic Tension: A different
stringbed measurement that utilizes vibration to measure stringbed stiffness.
The ERT 700 forces the string to vibrate back and forth and it measures
the vibration frequency. The higher the tension the faster the string
vibrates producing a higher pitch. If you drop tension, the string vibrates
more slowly and the pitch drops. This value is expressed in kiloponds.
Like the RDC this is an artificial scale that should be used as a reference
and not actual string bed tension. The ERT also calculates the tension
in pounds based upon the frequency response and a mathematical formula.
Values are presented in two scales. Dynamic Tension is ball power measured
in kiloponds required to depress the string bed 1 cm at the center point
of the stringbed. Dynamic tension measures the percentage of control
and power based upon a number of factors. The value is given as a percentage
based upon a scale from 0 to 100%.
-
Weight: The actual weight
of the unstrung and strung racquet. Weights are listed in ounces and
grams. Strung weight refers to the racquet ready to play with string
savers, vibration dampeners, head tape, etc. installed.
-
Balance: Values are given
for unstrung and strung balance. The actual static balance point of
the racquet. Balance is measured from two perspectives. The balance
in inches and millimeters measured from the handle of the frame. The
balance is also measured in points and inches from the centerline of
the frame.
-
Racquet flex: The amount
a racquet flexes along the longitudinal axis. The higher the value the
stiffer the frame. Unstrung and strung values are listed. Strung frames
are usually more flexible than unstrung frames. Most racquets range
from 40 to 85 on the RDC scale.
-
Pre-Stretch: The percentage
that the string is pre-stretched before settling on the indicated tension.
Strings can be pre-stretched from 5 to 20%. The type of string and its
construction usually dictates the percentage. Pre-stretching help reduces
the sometimes-dramatic tension loss of the first 48 hours after the
strings are installed. Pre-stretching also reduces coiling and kinking
producing higher quality and more consistent stringing.
-
Freshly Strung Racquet:
Racquets usually play different after being strung. Please allow a reasonable
amount of time for the strings to “settle-in.” This can
vary from several hours of actual play to several weeks, depending upon
individual player preferences.
- Unstrung
racquet length & width: The interior length &
width dimensions of the unstrung racquet head measured at two positions.
Values are given in inches and millimeters. These values serve as a
reference point when comparing them to the strung values.
-
Strung racquet length & width:
The interior length & width dimensions of the strung racquet head
measured at approximately 12 / 6, 3 / 9, o’clock positions. Values
are given in inches and centimeters. These values when compared to the
strung values are an indication of how much the frame is flexing and
aids in determining frame integrity. Frames usually flex no more than
.125 / 1/8 of an inch. Excessive variation usually indicates that the
graphite is possibly delaminating or breaking down in some manner.
-
SwingWeight: Swinging
and impacting a ball torques a racquet in three ways and each torque
rotates a racquet around a different axis. The resistance to rotation
around any axis is the “swing weight” around that axis.
Swing weight around the handle is simply called swing weight. This measures
the distribution of weight along the length of the racquet, which in
turn determines maneuverability, and stability along that axis when
you swing the racquet. Most tennis racquets fall between 200 and 400
kg·cm2.
The lower the value the more maneuverable the frame. Values are given
for unstrung and strung frames.
-
Twist Weight (Off-center stability):
Swing weight around an axis drawn from butt of the racquet to the head.
This measures weight distribution from side to side and its effect on
maneuverability and stability to twisting by you or the ball. The higher
the value the more stable when you hit a ball above or below the center
axis of the racquet. Values are expressed in kg·cm2
and range from 13 to 21. The majority of racquets fall between 13 and
17. Values given for strung racquet. A higher twist rate means less
energy of impact goes into pushing the racquet backwards or twisting.
The result is more comfort and power.
-
Recoil Weight (Shock resistance):
Swing weight around an axis parallel to the racquet face and through
the balance point (center of mass). This measures weight distribution
from the head of the racquet to the butt and its resulting resistance
to recoil. Values are expressed in kg·cm2.
Value given is for strung racquet. The higher the value the less shock
you feel. A higher recoil rate means less energy of impact goes into
pushing the racquet backwards or twisting. The result is more comfort
and power.
-
Hitting Weight (Effective Mass):
Although not actually one of the swingweights, Hitting Weight is important
because it shows the amount of the racquet’s mass actually involved
at the impact at any given location along the stringbed. If the ball
hits the racquet at the balance point (center of gravity) the racquet
behaves as its full mass. Anywhere else, it behaves as if the racquet
were lighter than its actual mass. At the tip, the hitting weight is
approximately 25% of the racquet’s total weight. At the center
of strings, it is about half. The hitting mass is important because
the power of the racquet at any given impact point depends on the hitting
mass at that point. More mass means more power. The impact point is
usually determined by the wear pattern of the strings.
- Hitting
Weight is presented in two forms;
one is the calculated weight in ounces and grams. The other is percentage
of weight being used based upon the impact area in relation to the
total racquet weight.
-
Center of Percussion (COP):
The center of percussion is that spot on the stringbed that produces
little to no shock in your arm or hand on impact with the ball. It is
generally located somewhere near the center of the stringbed, on the
center axis of the racquet. This is one of two "sweet spots"
on the racquet, the other of which is referred to as the node of the
racquet. The node is usually about 15 cm down from the tip of the racquet
(that is, higher on the racquet than the center of percussion). Generally
speaking, the higher the center of percussion, the more comfortable
the racquet will feel, because ball impacts between the COP and your
hand push the racquet into your hand, rather than pulling it out of
your hand, as do ball impacts above the node.
- Note:
This formula assumes that you are gripping the racquet handle in
such a way that your axis of rotation is 10 centimeters (4 inches)
from the butt end of the racquet.
-
Static Moment: The “feel”
of the racquet when you first hold the frame. Static moment refers to
how light or heavy the racquet “feels” when it is held stationary.
The higher the value, the heavier the racquet feels. Static moment can
be increased either by increasing the weight of the racquet, or moving
the balance point closer towards the handle or a combination of both.
Static moment is calculated by multiplying the weight of the racquet
by the distance of the balance point from the butt cap.
-
Power Rating: While it
is true there is no really accurate way to determine the power of any
given racquet static or otherwise. Our Power Formula takes into consideration
four major components, stiffness, swingweight, head size, and length
and gives you a useful approximate value to use in comparing racquet
power. These values range from 1600 to over 3900 with the majority falling
between 1800 and 3500. The median power rating is 2368. The higher the
power rating the more powerful the racquet.
- Racquet
Stability: A method to help determine your racquet’s
resistance against twisting in your hand. This measurement takes into
account the interior width of the racquet and the strung weight of the
racquet. These values usually range between 600 and 1200. Over-size
and/or heavier frames increase the racquets’ stability but decrease
the racquet’s maneuverability. The higher the value the greater
the stability. Generally speaking oversize and heavier racquets tend
to be more stable.
-
Power (RDC): Racquet power
is the speed the racquet gives the ball at the point of impact. This
is independent of variables such as: strength of the player, technical
skill, stroke length, swing speed and contact point. The level of power
is presented in two forms: 0 to 100 scale: the higher the number the
more powerful the racquet. Three letter categories: A best, B better,
and C good. Unstrung & strung vales are given.
- Control
(RDC): Control is the antithesis of power. Control is
the racquet’s ability to copy the direction and trajectory of
the ball at the moment of impact. The degree of control is measured
in two form: A 0 to 100 scale: the higher the number the greater the
control and a three letter category: A best, B better, and C good. Unstrung
& strung values are given.
-
Maneuverability (RDC):
This measurement represents the property that the frame possesses to
be moved through space. Maneuverability is dependent upon the distribution
of the weight, overall weight, and length. The degree of control is
measured in two scales: A 0 to 100 scale: the higher the number the
greater the control. Three
letter categories: A = excellent, B = satisfactory, and C = average.
Unstrung & strung vales are given.
Should
you have any questions please feel free to Contact
Us.
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Contact
Sandia
Racquet Services
Chip Brenn
3016 Camino de la Sierra NE
Albuquerque NM 87111
505-299-8052
Or
Email:
Chip@SandiaRacquetServices.com
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